Helminthiasis, the infestation of an animal by certain species of parasitic worms, is one of the most common, serious and widespread animal diseases. Of special interest are those parasitic worms of the family Trichostrongylidae and the genus Haemonchus. These parasites have the common name of twisted stomach worm and cause the diseases in ruminants known as haemonchosis, stomach worm disease or wireworm disease. These worms have been found to invade the abomasum of sheep, cattle, goats, moose, deer, bison and a number of other ruminants.
The above parasites during their maturation and growth have a very deleterious effect upon the animal and its rate of growth. In the abomasum, the parasites erode the epithelial tissues bringing about hemorrhage, anemia, weakness and tissue necrosis. Animals if they do not succumb to gross parasitism, are rendered economically unfit by weakness, lower vitality and poor growth and reproduction. The economic loss to the cattle and sheep industry of the United States from gross parasitism is extremely high.
While many drugs have been developed to try and offset the effects of these diseases, they have not been completely satisfactory for a variety of reasons. In some cases the drugs have not been sufficiently effective, and in others the cost of the drug has been too high and in many cases the parasites have developed a resistance to the drug.